ITTO20010566A1 - COMBUSTIBLE GAS SUPPLY DEVICE FOR AN ENDOTHERMAL ENGINE. - Google Patents

Description

DESCRIPTION

of the patent for industrial invention

The present invention refers to a fuel gas supply device for an internal combustion engine.

Due to air pollution and other health drawbacks produced by internal combustion engines fueled with liquid petroleum-derived fuels, and due to the cost of such fuels, fuel gas systems for engines have recently been developed, such as for example LPG or methane. To power the engine, the gas from the tank passes through a pressure reducer, which in the case of LPG causes it to vaporize. The vaporized gas, and / or at reduced pressure, is then mixed with the air and sent to the engine cylinders.

Normally in gas supply systems installed to power an internal combustion engine, the reducer-vaporizer unit is connected to the usual intake manifold, via a supply duct and an air-fuel mixing device. These fuel systems have the drawback of not dosing the fuel according to a correct and constant stoichiometric ratio, so the exhaust gases often contain quantities of pollutants, and the engines generally have less than optimal performance.

Various fuel gas feeding systems have been proposed, in which the gas leaving the reducer-vaporizer is sent to a distributor-metering unit.

distributor-metering unit, is connected to the intake ducts of the various cylinders by means of corresponding flexible ducts, so that these systems can be easily mounted as retrofitting. In a known system, the fuel gas is sent to the intake duct of each cylinder of the engine, by means of a multiple solenoid valve common to all the cylinders, which sends the metered gas to a manifold in communication with the intake ducts of all the cylinders. . The solenoid valve includes a group of shutters, each carried by an anchor of an electromagnet. In another known system, the fuel gas is sent to individual cylinders by means of corresponding separate solenoid valves.

In both cases, the anchor of each electromagnet is formed by an oblong plate that rotates around a contact line with an edge of a fixed element. This contact is ensured by a bar of elastic material acting on one end of the anchor plate, which is however held in the closed position of the solenoid valve by a corresponding spring acting at the shutter.

These solenoid valves have various drawbacks. First of all, the position of the contact line on the anchor may vary due to the machining and assembly tolerances of the parts. In addition, the presence of the closing spring of the solenoid valve makes the operation of the solenoid valve relatively slow. Finally, the solenoid valve is relatively expensive to manufacture, and particularly complicated assembly and maintenance.

Finally, a type of solenoid valve for pneumatic control circuits with compressed air is also known, the anchor of which is formed by an oblong plate, and has no return spring. The anchor is held in the closed position substantially by the air pressure in a chamber upstream of the compressed air outlet duct. This type of solenoid valve is not suitable for supplying fuel gas to an internal combustion engine, since the difference in fuel gas pressure between the inlet duct of the solenoid valve and the outlet is very small, generally less than 1 bar.

The purpose of the invention is to provide a fuel gas supply device for an internal combustion engine, which is highly reliable and of limited cost, and eliminates the drawbacks listed above for the prior art supply devices.

According to the invention, this object is achieved by a fuel gas supply device for an internal combustion engine, which comprises a solenoid valve adapted to be controlled to send the fuel gas to a corresponding cylinder of the engine, said solenoid valve comprising a duct 'inlet and at least one outlet duct of said combustible gas, a corresponding shutter carried by an anchor of a corresponding electromagnet being operable to put said inlet duct in communication with said outlet duct, said anchor being formed by an oblong rotatable plate around a line of contact with a fixed element, an elastic element acting on said plate so as to close said outlet duct by means of said shutter, and is characterized in that said contact line is formed by an edge of said plate with a flat surface of said fixed element.

For a better understanding of the invention, a preferred embodiment is described here, made by way of example with the aid of the attached drawings, in which:

Figure 1 is a diagram of part of a fuel system for an internal combustion engine, comprising a fuel gas supply device according to the invention;

Figure 2 is a section of a solenoid valve of the power supply device of Figure 1;

Figure 3 is a partial section along the line IΙ-IIΙ of Figure 2;

Figure 4 is a portion of the solenoid valve of Figure 2 on an enlarged scale;

Figure 5 is a schematic cross section of a variant of the solenoid valve of the power supply device of Figure 1;

Figure 6 is a partial section along the line VI-VI of Figure 5;

Figure 7 is a variant of a portion of Figure 4.

With reference to Figure 1, 5 generically indicates a fuel gas supply system, for example the usual LPG or methane, with an internal combustion engine 6, for example an eight cycle. The engine 6 can be of the four-cylinder type, each fed with air and fuel through a corresponding intake duct 7. The ducts 7 are fed with air from an air intake 8, through the usual air filter. The gas supply system 5 includes the usual gas pressure reducer 9. The reducer 9, through a conduit 10, is connected to the liquid gas tank, not shown in the figure.

The pressure reducer 9 is also in communication, through a delivery duct 11, with a fuel gas supply device, generally indicated by 12. The device 12 is able to send the combustible gas to the cylinders of the engine 6, for example through four flexible connection ducts 13, each of which is connected in a known way to the corresponding intake duct 7. The feeding device 12 is controlled in a phased and sequential manner by an electronic control unit 14, as a function of various signals corresponding to indicative values of the engine operation 6, such as engine speed and torque, throttle position, outside temperature and engine cooling water temperature.

The feeding device 12 comprises, for each cylinder of the engine 6, a solenoid valve 15 (Figure 2), which is enclosed in a box 20 formed by a pair of hollow bodies 16, 17. The two hollow bodies 16 and 17 are connected together along a plane P, in a known way, with the interposition of a gas-tight seal 18. The hollow body 16 is equipped with an inlet duct 19 having a threaded portion 21, able to be connected, through a fitting not shown in the figure, with the delivery duct 11 of the reducer 9 (see also Figure 1).

At least one control electromagnet 22 is housed in the hollow body 16, which comprises a core 23 of magnetic material and an electric coil 24. The core 23 is fixed on a bottom wall 25 of a sleeve 26 also of magnetic material, which is fixed in the hollow body 16 in a known way, with the interposition of a spacer plate 27, a plate 28 for supporting the electrical connections for the coil 24, and a pair of sealing gaskets 29. The spacer plate 27 has such a thickness to bring the surface of a terminal edge 30 of the sleeve 26 onto the plane P.

The hollow body 17 forms with the hollow body 16 a chamber 17a, which is in communication with the inlet duct 19 and with an outlet duct comprising a hole 31 carried by the hollow body 17, which will be better seen later. The chamber 17a is adapted to house a shutter 32 for the outlet duct. The shutter 32 is in the form of a disk of elastomeric material, and is carried in a known way by an anchor of the electromagnet 22, which is formed by an oblong plate 33 (see also Figure 3). In particular, the plate 23 has a flat surface 34, from which the shutter 32 protrudes towards the hole 31 of the outlet duct. The plate 33 is equipped with a pair of recesses 35 suitable for engaging two appendages 36, which are carried by a rib 37 of an anchor guide plate 38. The guide plate 38 is equipped with a hole 39 designed to be in alignment with the hole 31 of the hollow body 17, and is fixed inside the latter by means of screws 41.

According to the invention, the plate 33 is rotatable around a line of contact with the edge 30 of the sleeve 26. This contact line is formed by an edge 42 (Figure 4) of the plate 33 in contact with the flat surface of the edge 30 of the sleeve 26. The corner 42 is arranged between consisting of an inclined plane portion 43, and a flat surface 44 of the plate 33, opposite the surface 34. Preferably, the inclined plane 43 forms an angle a with the surface 44 of less than 20 °. In a seat 46 between the rib 37 of the plate 38 and a side wall of the hollow body 17 (see also Figure 2) there is an elastic bar 47 with a substantially circular section, made of elastomeric material, for example rubber. The bar 47 acts on a line L parallel to the edge 42 and has a diameter such as to create an elastic force F, which is sufficient to normally hold the shutter 32 in the closing position of the outlet duct.

Advantageously, the corner 42 is arranged on the surface 44 of the plate 33 in a position such that the lever arm of the force F of the bar 47 is at least one tenth of the lever arm of the center of the shutter 32. To avoid rapid deterioration of the surface of the edge 30, the corner 42 is rounded with a rounding radius R at least equal to the lever arm of the force F of the elastic bar 47. Furthermore, in order to optimize the efficiency of the action of the electromagnet 22 on the plate 33, it is it is advisable to arrange the surface of the edge 30 and of the core 23 in such a position that, when the shutter 32 is in the closed position, the angle β formed by the surface 44 of the plate 33 with the surface of the edge 30 is substantially equal to the angle formed by the inclined plane portion 43 with the same surface as the edge 30.

According to another aspect of the invention, the outlet duct of the solenoid valve 15 also comprises a calibrated nozzle 48, which is removably mounted in a seat formed by the hole 39 of the plate 38 and by a portion 49 of the hole 31, having increased diameter. In particular, the surface of the plate 38, facing the internal surface of the hollow body 17, has an annular groove 51 around the hole 39, in which an annular gas-tight seal 52 is inserted. The nozzle 48 is formed by a sleeve 53, the external surface of which has a shoulder 54 suitable for engaging the gasket 52.

The sleeve 53 is determined by two extreme edges 56 and 57, and is dimensioned in such a way that, when its edge 56 is positioned at the end of the stroke in the portion 49 of the hole 31, the shoulder 54 is arranged flush with the internal surface of the hollow body 17. In turn, the edge 57 is arranged flush with the surface of the plate 38 opposite to that in contact with the hollow body 17, or slightly protruding therefrom. The edge 57 has a rib 58 able to be engaged by the shutter 32, which under the action of the elastic bar 47 deforms, ensuring gas tightness when the solenoid valve 15 is closed.

<~> To mount the nozzle 48 in the hollow body 17, before mounting the plate 38, the nozzle 48 is inserted in the portion 49 of the hole 31, and the gasket 54 is placed on the shoulder 53. Then the plate is arranged 38 in the hollow body 17 so as to insert the nozzle 48 in the hole 39 of the plate 38. Finally, the plate 38 is fixed in the hollow body 17, screw the screws 41. Obviously, to replace a worn or damaged nozzle 48, it is first necessary to unscrew the screws 41, extract the plate 38 from the hollow body 17 and the nozzle 48 from the portion 49 of the hole 31.

According to another aspect of the invention, the supply solenoid valve 15 of each cylinder of the engine 6 comprises two distinct electromagnets 22, 22 '(see also Figure 3), which are substantially equal to each other and are contained in the same box 20 formed by the pair of hollow bodies 16 and 17. The two electromagnets 22, 22 'have the chamber 17a in common and receive the gas through the same inlet conduit of the hollow body 16. The two electromagnets 22, 22' are instead associated with two distinct outlet ducts, comprising two pairs of holes 31, 39 in the hollow body 17 and in the plate 38, and two corresponding calibrated nozzles 48 and 48 '.

A plate 61 equipped with a collector compartment 62 is fixed to the outside of the hollow body 17 by means of screws 59, which is adapted to receive the gas coming out of the two outlet holes 31 of the solenoid valve 15. The compartment 62 has a recess 63 adapted to house a gas-tight seal 64. The plate 61 is also provided with a threaded hole 66, in which an end fitting of the connection duct 13 can be screwed with the supply duct 7 of the corresponding cylinder of the engine 6.

Advantageously, the two calibrated nozzles 48 and 48 'can have an equal external shape, and an internal diameter different from each other, in order to allow a different gas flow rate. The two holes 31 can have a diameter equal to each other and at least equal to the greater-of-the-internal diameters of the two nozzles 48 and 48 '. In particular, the internal diameter of the nozzle 48 'can be chosen in such a way as to obtain a gas passage section double that of the calibrated nozzle 48. The control unit 11 is adapted to actuate the solenoid valves 15 selectively according to the operating conditions of the motor 6. The control unit 14 is also adapted to generate control pulses of modulated width, so as to control each electromagnet 22, 22 'with modulation of the width of the pulses, known as PWM. In this way, the control unit 14 causes one or both of the switches 32 of each solenoid valve 15 to open for a variable time, within the feeding phase of the corresponding cylinder of the engine 6, so that the engine 6 has a considerable operating flexibility.

To power the motor 6, a corresponding solenoid valve 15 can be provided for each cylinder, equipped with an electromagnet 22, or a pair of electromagnets 22, 22 '. Advantageously, a feeding device 12 can be provided for all the cylinders of the engine, in which a number of solenoid valves 15 equal to the number of cylinders of the engine 6, or to a submultiple of this number of cylinders, is integrated.

Figures 5 and 6 schematically illustrate a power supply device 12 for the four-cylinder engine 6, in which the four solenoid valves 15, each comprising a pair of electromagnets 22, 22 'are integrated into a single body. The electromagnets 22, 22 'are substantially the same as those shown in Figures 2-4, so they will not be described further. In particular, in this power supply device, all the electromagnets 22, 22 'are aligned in a single row and are enclosed in a single box 68, comprising a hollow body 69, in which the eight electromagnets 22, 22' are housed. . These are mounted with the interposition of a common spacer plate 71, and a plate 72 on which the electrical connections of the corresponding pins 73 are arranged.

The hollow body 69 is provided with a common conduit 74 for all the solenoid valves 15, which comprises a portion 76 parallel to the plates 71 and 72, and a portion 77 perpendicular to these plates 71 and 72. The portion 76 has an end 78 adapted to be connected to the delivery duct 11 (see also Figure 1) of the pressure reducer 9. The portion 77 is in communication with a chamber 79 common to all the solenoid valves 15.

The box 68 also comprises a second hollow body 81, connected to the hollow body 69 along a plane P and with the interposition of a common gasket 80. A guide plate 82 is fixed in the hollow body 81 by means of screws not visible in the drawings. of the plates 33 of the anchors of the electromagnets 22. The plate 82 is equipped as standard with a pair of appendages 36 on which the recesses 35 of the plates 33 engage. The hollow body 81 and the plate 82 carry the pairs of nozzles 48, 48 ' of the output ducts of the individual solenoid valves. 15, 15 ', similarly to the feeding device 12 of Figures 2 and 3. The appendages 36 are carried by a single rib 83, which defines a seat 84 for a single elastic bar 86 common for all the plates 33.

The box 68 finally comprises a closing plate 87, which is fixed to the two hollow bodies 69 and 81 by means of a pair of screws 88. The plate 87 is equipped with four manifold compartments 89, each suitable for receiving the gas fed under the control of the corresponding pair of electromagnets 22, 22 '. Each compartment 89 communicates with a hole 91, in which the fitting of the connection duct 13 of the corresponding cylinder of the engine 6 can be fixed.

According to the variant of Figure 7, the edge 42 of the plate 33 of the anchor of the electromagnet 22 is kept in contact with the surface of the edge 30, instead of by the elastic bar 47 or 86, by a leaf spring 92, which is fixed on guide plate 38 or 82 in any known way. In this case, the rib 37 can have reduced thickness or be eliminated, as indicated in Figure 7.

From what has been seen above, the advantages of the fuel gas feeding device according to the invention are evident, compared to the feeding devices of the known art. In particular, thanks to the edge arranged on the surface of the plate 33 of the anchor, the wear of the line of contact with the edge 30 is eliminated, and the frictions of the relative movements are reduced, so that a high speed and precision of the actuation of the solenoid valve. In addition, any manufacturing and assembly tolerances of the parts, and in particular of the hollow bodies 16, 17 and 69, 81 leave the length of the shutter lever arm 33 unchanged.

The greater length of the lever arm of the force F of the elastic bar 47, 86 also avoids the need for additional return springs, simplifying the manufacture of the feeding device. In turn, the use of more than one electromagnet 22, 22 ', to control corresponding nozzles 48, 48 to power each cylinder of the engine 6, makes the operation of the engine 6 more flexible, while the use of nozzles 48, 48 'replaceable, greatly increases the life of the power supply. Finally, the common feeding device of Figures 5 and 6 also allows a great compactness of the unit and enormously reduces the manufacturing cost of the device itself.

It is understood that various modifications and improvements can be made to the power supply devices described without departing from the scope of the claims. For example, the shape of the electromagnet and the relative plate 33 of the anchor can be varied. Furthermore, the leaf spring 92 can be replaced by a helical spring.

The power supply device 12 can be designed in a modular way, and such as to allow the reciprocal connection of a variable number of modules to obtain a single power supply group. Furthermore, the ends of the inlet and outlet conduits 19, 66 and 78, 91 can be configured to be connected to the respective conduits in any known way.

In the case of separate solenoid valves 15 for each cylinder of the engine, they can be fixed directly on the intake ducts 7 with simple fittings, without the need for the connection ducts 13. More than two electromagnets can also be provided for the solenoid valve of each cylinder of the motor, which can be arranged in the box 20 in any reciprocal position. Finally, in the common power supply device, the solenoid valves 15 and / or the electromagnets 22, 22 'can be arranged in two or more rows.

Claims (21)

R I V E N D I C A Z I O N I 1. Fuel gas supply device for an internal combustion engine, comprising at least one solenoid valve (15) adapted to be controlled to send the fuel gas to a corresponding cylinder of the engine, said solenoid valve (15) comprising an inlet duct (19 , 74) and at least one outlet conduit (31, 48; 31, 48 ') of said combustible gas, a corresponding shutter (32) carried by an anchor (33) being operated by a corresponding electromagnet (22, 22') to put said inlet conduit (19, 74) in communication with said outlet conduit (31, 48; 31, 48 '), said anchor being formed by an oblong plate (33) rotatable around a contact line (42) with a fixed element (26), an elastic element (47, 86, 92) acting on said plate (33) so as to close said outlet duct (31, 48; 31, 48 ') by means of said shutter (32), characterized in that said contact line is formed by an edge (42) of said plate na (33) in contact with a flat surface (30) of said fixed element (26). 2. Feeding device according to claim 1, characterized in that said edge (42) is arranged between a first surface (44) of said plate (33) and an inclined plane portion (43), said shutter (32) being arranged on a second surface (34) of said plate (33) opposite to said first surface (44). 3. Feeding device according to claim 2, characterized in that said elastic element is formed by a bar (47, 86) of elastomeric material, acting on said second surface (34) in correspondence with said inclined plane portion (43) along a line (L) parallel to said edge (42). 4. Feeding device according to claim 2, characterized in that said elastic element is formed by a leaf spring (92), acting on said second surface (34) in correspondence with said inclined plane portion (43) along a line (L) parallel to said edge (42) 5. Feeding device according to claim 3 or 4, characterized in that said shutter is in the form of a disk (33), said parallel line (L) forming with said edge (42) a lever arm of at least one tenth of the lever arm formed by said disk (32). 6. Feeding device according to claim 5, characterized in that said inclined plane portion (43) forms with said first surface (44) an angle (a) of less than 20 °, said edge (42) being rounded with a radius of rounding (R) at least equal to the lever arm of said parallel line (L). 7. Feeding device according to claim 6, characterized in that said flat surface being arranged first surface (44) forms in use with said flat surface (30) an angle (β) substantially equal to that of said inclined plane portion ( 43) with said flat surface (30). 8. Power supply device according to one of the preceding claims, characterized in that said solenoid valve (15) is enclosed in a box (20, 68) comprising two hollow bodies (16, 17; 69, 81) connected together in a gas-tight manner along a plane (P) perpendicular to said outlet conduit (31, 48; 31, 48 '), a first of said hollow bodies (16, 69) being equipped with said inlet conduit (19, 74) and housing said electromagnet (22, 22 '), said surface (30) of said fixed element (26) being parallel to said plane (P). 9. Power supply device according to claim 8, wherein said electromagnet (22, 22 ') comprises a magnetic core (23), characterized in that a second of said hollow bodies (17, 81) is provided with said outlet conduit (31, 48; 31, 48 ') and houses said anchor (33), said fixed element (26) being carried by said magnetic core (23). 10. Feeding device according to claim 8 or 9, characterized in that said outlet duct (31, 48; 31, 48 ') comprises a calibrated nozzle (48, 48') removably mounted in a seat (49) of said second hollow body (17, 81). 11. Feeding device according to claim 10, characterized in that the plate (33) of said anchor is carried by a guide plate (38, 82) fixed on said second hollow body (17, 81), said nozzle (48 , 48 ') being provided with a gas-tight portion inserted in a corresponding hole (39) of said guide plate (38, 82), said elastic bar (47, 86) being housed in a seat formed between said second body cable (17, 81) and said guide plate (38, 82). Feeding device according to one of claims 8 to 11, characterized in that said solenoid valve (15) comprises at least two electromagnets (22, 22 ') adapted to control two corresponding outlet ducts (31, 48; 31, 48') ) arranged in said second hollow body (17, 81), said outlet conduits (31, 48; 31, 48 ') being substantially parallel to each other. 13. Feeding device according to claim 12, characterized in that another body (61, 83) is gas-tight connected to said second hollow body (17, 81), said other body (61, 83) being equipped with a manifold compartment (62, 89) in communication with said outlet conduits (31, 48; 31, 48 '), said manifold compartment (62, 89) also being in communication with the corresponding cylinder of the engine. 14. Feeding device according to claim 12 or 13, characterized by the fact that said outlet ducts (31, 48; 31, 48 ') are equipped with nozzles (48, 48') having different internal diameters. Feeding device according to one of claims 12 to 14, characterized in that the plates (33) of said anchors are carried by a common guide plate (47, 82), each of said nozzles (48, 48 ') being inserted gas-tight in a corresponding seat (39) of said guide plate (38, 82). Power supply device according to one of claims 12 to 15, characterized in that said electromagnets (22, 22 ') are controlled selectively and in phase with corresponding pulses of modulated width (PWM), which are generated by a unit control electronics under the control of signals indicative of engine operation. Feeding device according to one of claims 12 to 16, characterized in that a solenoid valve (15) is provided for each cylinder of the engine, the solenoid valves (15) of at least two cylinders having said first hollow body (69) in common ) and said second hollow body (81). 18. Feeding device according to claims 14 and 17, characterized in that the nozzles (48, 48 ') corresponding to said electromagnets (22, 22') being arranged along a single row, said other body (87) being common for said solenoid valves (15) and being provided with a manifold compartment (89) for each of said solenoid valves (15). 19. Feeding device according to claim 18, characterized by the fact that said elastic bar (86) is common to the plates (33) of the anchors of said electromagnets (22, 22 '). 20. Power supply device according to claim 16 and one of claims 17 to 19, characterized in that said electromagnets (22, 22 ') of said valves (15) are controlled by said electronic unit sequentially and in phase with the operation of the corresponding engine cylinders. 21. Fuel gas feeding device for an internal combustion engine, substantially as described with reference to the attached drawings.